/Engine/Source/Runtime/StaticMeshDescription/Public/StaticMeshOperations.h
Recompute any invalid normal, tangent or Bi-Normal for every vertex in the mesh description with the given options. If the EComputeNTBsFlags Normals or Tangents are set, the corresponding data will be force-recomputed.
static void ComputeTangentsAndNormals ( [FMeshDescription](API\Runtime\MeshDescription\FMeshDescription) & MeshDescription, EComputeNTBsFlags ComputeNTBsOptions )